Management technique of friction coefficient based on surface roughness, substrate for information recording medium, information recording medium and manufacture method thereof

Abstract

There are disclosed an information recording medium substrate having a surface roughness of Rmax 15 nm or less, and an information recording medium, particularly an information recording medium substrate and information recording medium in which for surfaces of the substrate and medium, a bearing area value (offset bearing area value) in a depth of 0.5 to 5 nm (predetermined slice level) from a bearing height (real peak height) corresponding to the bearing area value of 0.2% to 1.0% is 90% or less, and a manufacture method of the substrate and medium.

What is claimed is:  
     
       1. A substrate for a magnetic recording medium having a surface roughness of Rmax 15 nm or less, 
       wherein for the surface of said substrate, an offset bearing area value of the surface roughness is 90% or less, where the offset bearing area value is a bearing area value at a slice level predetermined in a depth of 0.5 to 5 nm from a bearing height (real peak height) corresponding to a bearing area value of 0.2% to 1.0%.  
     
     
       2. A substrate for a magnetic recording medium having a surface roughness of Rmax 15 nm or less, 
       wherein for the surface of said substrate, an offset bearing area value of the surface roughness is 90% or less, where the offset bearing area value is a bearing area value at a slice level set in a depth corresponding to 20 to 45% of Rmax from a bearing height (real peak height) corresponding to a bearing area value of 0.2% to 1.0%.  
     
     
       3. The substrate for a magnetic recording medium according to  claim 1 , or  2 , wherein the offset bearing area value of the surface roughness is 40%±20%. 
     
     
       4. The substrate for a magnetic recording medium according to  claim 1 , or  2 , wherein the offset bearing area value of the surface roughness is 70%±20%. 
     
     
       5. The substrate for a magnetic recording medium according to  claim 1 , or  2 , wherein the offset bearing area value is a bearing area value at a slice level predetermined in a depth of 3 nm from a bearing height (real peak height) corresponding to a bearing area value of 0.5%. 
     
     
       6. The substrate for a magnetic recording medium according to  claim 1 , or  2 , wherein said surface roughness is measured with an AFM (atomic force microscope). 
     
     
       7. The substrate for a magnetic recording medium according to  claim 1 , or  2 , wherein said substrate for a magnetic recording medium is a glass substrate whose surface is subjected to precision polishing and/or etching treatment. 
     
     
       8. A magnetic recording medium, 
       wherein a magnetic layer is formed on the substrate for a magnetic recording medium according to  claim 1 , or  2 .  
     
     
       9. A magnetic recording medium having a surface roughness of Rmax 15 nm or less on a medium surface, 
       wherein for the medium surface of said magnetic recording medium, an offset bearing area value of the surface roughness is 90% or less, where the offset bearing area value is a bearing area value at a slice level predetermined in a depth of 0.5 to 5 nm from a bearing height (real peak height) corresponding to a bearing area value of 0.2% to 1.0%.  
     
     
       10. A magnetic recording medium having a surface roughness of Rmax 15 nm or less on a medium surface, 
       wherein for the medium surface of said magnetic recording medium, an offset bearing area value of the surface roughness is 90% or less, where the offset bearing area value is a bearing area value at a slice level set in a depth corresponding to 20 to 45% of Rmax from a bearing height (real peak height) corresponding to a bearing area value of 0.2% to 1.0%.  
     
     
       11. The magnetic recording medium according to  claim 9  or  10 , 
       wherein the offset bearing area value is 40%±20%.  
     
     
       12. The magnetic recording medium according to  claim 9  or  10 , 
       wherein the offset bearing area value is 70%±20%.  
     
     
       13. The magnetic recording medium according to  claim 9  or  10 , 
       wherein the offset bearing value is a bearing area value at a slice level predetermined in a depth of 3 nm from a bearing height (real peak height) corresponding to a bearing area value of 0.5%.  
     
     
       14. The magnetic recording medium according to  claim 9  or  10 , 
       wherein said surface roughness is measured with an AFM (atomic force microscope).  
     
     
       15. The magnetic recording medium according to claims  9  or  10 , 
       wherein a friction coefficient based on the surface roughness of the medium surface is 3 or less.  
     
     
       16. The magnetic recording medium according to  claim 9  or  10 , 
       wherein a correlation of a friction coefficient in the magnetic recording medium with various lubricants formed thereon with an offset bearing area is checked, and the lubricant with a reduced friction force by the lubricant is employed.  
     
     
       17. The magnetic recording medium according to  claim 16 , 
       wherein said lubricant is a lubricant classified in perfluoro alkylpolyether (PFPE), including ether joining in a main chain, having —(OCF 2 F 2 ) m (OCF 2 ) n — straight chain structure, and having a hydroxyl group as a terminal group.  
     
     
       18. The magnetic recording medium according to  claim 15 , 
       wherein a correlation of the friction coefficient in the magnetic recording medium with various lubricants formed thereon with an offset bearing area is checked, and the lubricant with a reduced friction force by the lubricant is employed.  
     
     
       19. The magnetic recording medium according to  claim 18 , 
       wherein said lubricant is a lubricant classified in perfluoro alkylpolyether (PFPE), including ether joining in a main chain, having —(OCF 2 F 2 ) m (OCF 2 ) n — straight chain structure, and having a hydroxyl group as a terminal group.